title: Transmission electron microscopy studies of NaLaMgWO6: spontaneous formation of compositionally modulated stripes.
abstract: Transmission electron microscopy studies of the perovskite NaLaMgWO 6 reveal the formation of a complex, compositionally modulated structure. Annular dark field scanning transmission electron microscopy images and scanning transmission electron microscopy-electron energy-loss spectroscopy scans show that this modulation involves a repeating pattern of La-rich and La-poor stripes, each stripe 6 a p or approximately 24 A wide (where a p is the edge length of the simple cubic perovskite unit cell). High-resolution transmission electron microscopy images clearly show, and electron diffraction patterns confirm, a periodicity of 12 a p along either the [100] p or [010] p direction. Available evidence suggests a spontaneous separation into stripes that possess the nominal stoichiometry, NaLaMgWO 6, alternating with Na-poor/La-rich stripes that have a stoichiometry of (La x Na 1-3 x )LaMgWO 6. X-ray powder diffraction measurements are insensitive to this intricate structural complexity, which may be a more widespread feature of (A (+)Ln (3+))MM'O 6 perovskites than previously appreciated.
authors.affiliation: Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense, Madrid-28040, Spain. sgmartin@quim.ucm.es
authors.forename: Susana
authors.initials: S
authors.lastname: García-Martín
authors.forename: Esteban
authors.initials: E
authors.lastname: Urones-Garrote
authors.forename: Meghan C
authors.initials: MC
authors.lastname: Knapp
authors.forename: Graham
authors.initials: G
authors.lastname: King
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Woodward